Date: Mon, 07 Jul 2008 15:17:22 -0700 From: Julian Elischer <julian@elischer.org> To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: FreeBSD Net <freebsd-net@freebsd.org> Subject: Re: Freebsd IP Forwarding performance (question, and some info) [7-stable, current, em, smp] Message-ID: <487295F2.7070802@elischer.org> In-Reply-To: <20080707221257.GH62764@server.vk2pj.dyndns.org> References: <2d3001c8def1$f4309b90$020b000a@bartwrkstxp> <486FFF70.3090402@gtcomm.net> <48701921.7090107@gtcomm.net> <4871E618.1080500@freebsd.org> <20080708002228.G680@besplex.bde.org> <48724238.2020103@freebsd.org> <20080708034304.R21502@delplex.bde.org> <20080708045135.V1022@besplex.bde.org> <ed91d4a80807071227q5d9ca283g59270a1ab92c80a9@mail.gmail.com> <48727BA9.6020702@elischer.org> <20080707221257.GH62764@server.vk2pj.dyndns.org>
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Peter Jeremy wrote: > On 2008-Jul-07 13:25:13 -0700, Julian Elischer <julian@elischer.org> wrote: >> what you need is a speculative prefetch where you an tell teh >> processor "We will probably need the following address so start >> getting it while we go do other stuff". > > This looks like the PREFETCH instructions that exist in at least amd64 > and SPARC. Unfortunately, their optimal use is very implementation- > dependent and the AMD documentation suggests that incorrect use can > degrade performance. > It might be worth looking to see if the network processing threads might be able to prefetch the IP header at least :-)
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